Air-dried coatings based on aqueous polymeric emulsions are widely used in industrial applications. It is known that the properties of these polymers can be modified by bonding metals to the polymer molecules. Bonding the metal to the polymer is typically attained by the formation of ionic bonds. In ionic bonding, the metals are usually bonded to an ionic group in the polymer such as a carboxylic acid group. The ionically bonded polymers, however tend to lose their structural stability in polar solvents, such as water or alcohol, and at high temperatures. Thus, polymeric coatings and adhesives which are crosslinked through ionic bonding are subject to attack and deterioration by chemical solvents, moisture and by thermal degradation.
Polymeric compositions which are ionically crosslinked are disclosed in U.S. Pat. Nos. 3,740,366; 3,322,734; and 2,754,280. The '366 patent teaches pressure sensitive adhesives ionically crosslinked by a polyvalent metal and free carboxylic acid groups. The '734 patent teaches ionically crosslinked copolymers containing ionized carboxyls or ionized sulfonyls and metal ions as an ionic linking agent. The '280 patent disclosed emulsions of ionically cross-linked resins wherein pairs of carboxyl groups in the molecular chains are crosslinked by atoms of polyvalent metals.
The prior art compositions based on carboxyl/polyvalent metal cross-linking have disadvantages in many properties such as solvent resistance, print resistance, block resistance, storage stability and adhesion. Attempts have been made to improve the properties of polymeric coating and adhesive compositions by incorporating therein phosphorous-containing polymers.
British Patent Specification No. 958,856 discloses copolymers suitable for use in coating compositions which are derived from (1) esters of acrylic or methacrylic acid; (2) a methylol compound; and (3) a mixed ester of a diol esterified with (meth)acrylic acid and an organic or inorganic acid (such as phosphoric acid).
U.S. Pat. No. 3,449,303 discloses polymers of phosphate esters derived from allyloxy and allyloxyalkoxy phosphates and having improved dyeability.
U.S. Pat. No. 4,110,285 discloses a process for preparing a stable aqueous emulsion of addition polymers using a mixture of phosphate esters as an emulsion stabilizer during the polymerization process.
European patent publication no. 0221498 discloses anticorrosive copolymer emulsion prepared from ethylenically unsaturated monomers and a polymerizable surface-active alkylphosphate monomer.
U.S. Pat. No. 4,477,623 disclosed an improved paint composition comprising; (1) a water-insoluble addition polymer prepared from styrenes, acrylates, methacrylates, vinyl esters and vinyl chloride (including at least one monomer containing a phosphoric, sulphonic or carboxylic acid group (2) anionic or non-ionic emulsifier, (3) polyoxyethylene-chain-containing compound and (4) alkali-soluble addition polymer.
U.S. Pat. No. 4,506,057 discloses a modified latex composition comprising at least one ethylenically unsaturated monomer and a compound having a-PO(O).sub.2 group which is bound to the surface of the latex. These compositions may contain various water-insoluble inorganic fillers such as zinc oxide.
Japanese patent disclosure no. 61-143411 discloses an acrylic coating material consisting of a copolymer of 90-99.9 wt. % of copolymerizable monomer and 0.1-10 wt. % of phosphoric acid ester.
U.S. Pat. No. 4,658,003 discloses polymeric compositions comprising the reaction product of 0.5-100% of a (hydroxyl)-phosphinyl-alkyl acrylate or methacrylate and 0-99.5% of a methacrylate and 0-99.5% of a polymerizable 1,2-ethylencially unsaturated compound.
The present invention is an improvement over the prior art compositions of carboxyl or phosphorus-containing polymers. The improvement lies in the combination of one or more polymer(s) containing phosphorus groups and a crosslinking agent comprising one or more water-soluble polyvalent metal compounds. It is an object of this invention to provide coating and adhesive compositions which have improved solvent, chemical, print and corrosion resistance and adhesion to metal. It is a further object of this invention to provide improved phosphorus-containing polymer compositions which contain water-soluble polyvalent metal crosslinking agents instead of water-insoluble metal crosslinkers. It is an even further object of this invention to provide novel polymeric compositions which are curable at ambient temperatures. Further, it is an object of the present invention to provide film-forming polymeric compositions which are stable as a one-container system without the necessity of premixing of ingredients immediately prior to use.